Systems and methods for monitoring underwater structures

ABSTRACT

Systems and methods for monitoring underwater structures are provided. First and second sets of point cloud data that are obtained at different times are compared to determine whether the location of the underwater structure has changed. For detecting vibration, a series of range measurements taken along a line intersecting the underwater structure are compared to one another to determine an amplitude and frequency of any vibration present in the underwater structure. For detecting temperature, the ratio of different components of return signals obtained from a point in the water surrounding the underwater structure is measured to derive the temperature of the water. Leak detection can be performed by scanning areas around the underwater structure. Monitoring systems can include a primary receiver for range measurements, and first and second temperature channel receivers for temperature measurements.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/971,108, filed May 4, 2018, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/501,487, filed May 4, 2017,the entire disclosures of each of which are hereby incorporated hereinby reference. The present application is related to U.S. patentapplication Ser. No. 16/365,848, filed Mar. 27, 2019, now U.S. Pat. No.10,698,112, which is also a continuation of U.S. patent application Ser.No. 15/971,108, filed May 4, 2018, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/501,487, filed May 4, 2017.

FIELD

The present disclosure is directed to methods and systems for monitoringunderwater installations and in particular to non-contact monitoring ofunderwater structures and equipment.

BACKGROUND

Monitoring underwater equipment, such as wellheads, manifolds, risers,anchors, Pipeline End Terminations (PLETS), Blow Out Preventors (BOPs),pumps, touch down points, suction piles, chains, slip joints, andpipelines is important to ensuring the safe and reliable operation ofsuch equipment. Through environmental and/or operational conditions,such underwater equipment can experience undesirable movement, vibrationconditions, and temperature differentials. For example, vortex-inducedvibration (VIV) is responsible for the majority of the fatigue damage indeep water drilling risers. Damage from VIV is a major issue and ispotentially very dangerous for operational personnel and theenvironment.

Conventional techniques for detecting and monitoring movement andvibration require the installation of vibration, accelerometers, and/ormotion sensors directly on the equipment to be monitored. Accordingly,available systems require that they be physically attached to theequipment, either by integrating a monitoring device into the equipmentprior to putting the equipment in operation, or by attaching themonitoring device to the equipment while that equipment is in place.Moreover, each underwater structure to be monitored requires its ownvibration, accelerometer, and/or motion sensor.

External temperature variations of subsea components are an indicationof internal issues within the system. For instance, hot spots canindicate cracks in insulation, overheating pumps, thinning of internalpipe walls, or other problems. Cold spots can indicate hydrateformations inside pipes or equipment that either reduce or totally blockflow, and other problems. Currently the only way to measure thesetemperature deltas are with point probes either attached to the subseaequipment or carried by a diver or remote vehicle. This provides a verysparse temperature “map” with many gaps.

In addition, access to equipment installed on the seafloor can bedifficult, and the installation of additional devices directly on themonitored equipment poses the risk of damaging that subsea equipment.The devices installed must be connected to subsea power sources, or havebatteries installed (which requires periodic changing). The datarecorded by the devices must be downloaded periodically, which typicallyrequires a direct connection for large amounts of data. Both of thesescenarios require contact of the subsea equipment by divers, RemoteOperated Vehicles (ROVs), or Autonomous Underwater Vehicles (AUVs),which is costly and risks damaging expensive subsea equipment.Accordingly, it would be desirable to provide systems and methods thatallowed for the monitoring of underwater equipment, without requiringmonitors that are directly attached to such equipment, and preferably asingle monitoring device to provide multiple monitoring functions.

SUMMARY

The present disclosure provides devices, systems and methods for themonitoring of any and all-natural underwater structures or equipmentinstalled underwater. In particular, it includes any and all equipmentinstalled subsea for an oil or gas field and the accompanying seabed.This includes, but is not limited to, an entire subsea tree system,subsea manifold, PLET, BOP, pipelines and flow lines, anchors, risers,touch down points, suction piles, chains, slip joints, subsea processingsystems, and the interconnectivity jumpers from the well to the surfacedelivery connection and surrounding seafloor. The described methods andsystems increase the performance and integrity of the well monitoringsolution during drilling, reservoir stimulation, well intervention,riserless well intervention, well pressure testing, and during plug andabandonment operations. The described methods and devices utilize one ormore non-touch subsea optical systems (including laser systems) forsubsea well and subsea infrastructure measurements and monitoring.Monitoring of underwater systems can include monitoring shifts inlocation over time, vibrations, temperature, and/or leaks. This includesbut is not limited to vibrations caused by operating or environmentalconditions, fluid leaks, and other dynamic conditions related to themonitored systems.

Systems in accordance with embodiments of the present disclosure caninclude various optical sensors provided as part of active, light-basedmetrology systems or sensors. In accordance with at least someembodiments of the present disclosure, a monitoring system is providedthat includes a light detection and ranging system (hereinafter “lidar”)monitoring device. In such embodiments, the lidar device can be in theform of a scanning lidar, flash lidar, pulsed laser lidar, amplitudemodulated continuous wave (AMCW) phase detection lidar, chirped AMCWlidar, amplitude frequency modulated continuous wave (FMCW) lidar, trueFMCW lidar, pulse modulation code, or other lidar system. Moreover, thelidar system can incorporate a pulsed or modulated continuous wave laserlight source. Other embodiments can include a monitoring systemincorporating a laser triangulation, photometric stereo, stereoscopicvision, structured light, photoclinometry, stereo-photoclinometry,holographic, digital holographic, or other device that uses light tosense 3-D space. The monitoring system is placed in the vicinity of theequipment to be monitored. In accordance with embodiments of the presentdisclosure, multiple pieces of equipment can be monitored by a singlemonitoring system. In accordance with further embodiments of the presentdisclosure, multiple monitoring systems are used in combination tomonitor one or more pieces of subsea equipment. In accordance with stillother embodiments of the present disclosure, targets, such as laserscanning targets, three-dimensional spherical targets, lidar targets, orother target indicia or structures can be attached to the monitoreddevices and observed by one or more monitoring systems.

In operation for displacement measurements, a monitoring system asdisclosed herein makes a rapid number of range, angle, angle, andintensity measurements of the monitored equipment or other underwaterstructure in relation to the laser monitoring system itself, otherpieces of equipment, monuments, or other “known” points in space, thusproducing a set of point cloud data comprising a 3-D scan of theunderwater scene. Alternately, the monitoring system makes a rapidnumber of range, angle, angle, and intensity measurements of specifictargets mounted on the monitored equipment in relation to specifictargets mounted on other pieces of equipment, monuments, or other“known” points in space. Change detection is performed on the pointcloud data, which may comprise time stamped X, Y, Z, intensity datasets,to determine if movement of the monitored underwater structure hasoccurred over a selected time span (which can vary from under a minuteto over a year). As opposed to a single spot lidar, multiple singlespots can be scanned simultaneously. Alternately, a laser line scansystem, triangulation sensor, structured light sensor, flash lidar, orother light-based metrology system could be used to make the range,angle, angle, and intensity measurements. As yet another alternative,scans can be taken from multiple optical or lidar devices simultaneouslyor in a time coordinated manner.

In operation for vibration measurements, the monitoring system makes arapid number of range, angle, angle, intensity measurements of a scenecontaining an underwater structure, thus producing a set of point clouddata. A particular location or locations on the underwater structure arethen selected, and a rapid number of range, angle, angle, intensitymeasurements are made relative to a selected location in series. Thetiming of the range measurements is accurately recorded. Using the rangeand time measurements, vibration displacement (direct measurement) andfrequency content (through a Fourier Transform or other calculation) canbe calculated. A single spot sensor (such as a scanning lidar) can beprogramed to measure multiple locations in a fast succession in order toobtain vibration distance and frequency information at multiple knownlocations on the underwater structure at virtually the same time. Thiscan then be used to calculate the vibration mode of the underwaterstructure. As a further alternative, a laser line scan system,triangulation sensor, structured light sensor, or flash lidar could beused to make range, angle, angle measurement on multiple pointssimultaneously. As yet another alternative, scans can be taken frommultiple optical or lidar devices simultaneously or in a timecoordinated manner.

In operation for temperature measurements, the monitoring system makes arapid number of range, angle, angle, intensity measurements of themonitored underwater structure, thus producing an initial wide area 3-Dscan that is quickly processed and displayed on the user screen. Thisinitial image is used to identify target areas of interest for making aseries of temperature measurements and can be created by 3-D data (rangedata) or 2-D data (just the intensity of the 3-D data). In either casethe azimuth, elevation, and range locations are known for each point andcan be used to revisit those exact locations on the target fortemperature measurements taken from the water surrounding or near thoselocations. In particular, the temperature of the water is determined bythe ratio of returned light of different wavelengths or polarizations.Note that this is significantly different from alternative systems forunderwater temperature measurements. In those other systems the goal wasto measure the general water temperature, so accurate location and rangeof the temperature measurement was not critical. When monitoringtemperatures of equipment and subsea structures, one must be able toaccurately select the location of the measurement in angle and range.The systems and methods of the current disclosure provide an accurateand repeatable method for selecting the angular and range location ofwhere the temperature measurement is to be taken, thus allowingmonitoring of specific locations upon a structure.

In a leak detection mode, the monitoring system is directed so that ittakes range and intensity measurements along a direction at or towardsan underwater structure or area being monitored. In accordance with atleast some embodiments, the direction may be at or towards a controlpoint. A leak is detected as a plume of liquid or gas bubbles having adensity that is different than the underwater structure or thesurrounding water. This difference in density can be detected as adifference in the strength (i.e. the intensity) of the return signalreceived by the monitoring system.

Advantages over current methods for vibration, motion, temperaturemeasurements, and leak detection include enabling non-touch measurementsand reduced tooling. Using an optical metrology system such as a lidardevice reduces the installation time as compared to clamped tooling andsubsea logged data recovery, and removes the risk associated withtouching the subsea structures. The monitoring system of the presentdisclosure can be temporarily installed for short term monitoring, orpermanently installed for long term monitoring of a subsea structure.

Additional features and advantages of embodiments of the presentdisclosure will become more readily apparent from the followingdescription, particularly when taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example drilling and production system, the componentsof which can be monitored using systems and methods in accordance withembodiments of the present disclosure;

FIG. 2 depicts examples of components to be monitored by one or moremonitoring systems in accordance with embodiments of the presentdisclosure;

FIG. 3 depicts the components to be monitored of FIG. 2, together withmonitoring systems and installed monuments and targets;

FIG. 4A depicts 3-D targets in accordance with embodiments of thepresent disclosure;

FIG. 4B depicts 3-D targets in a point cloud in accordance withembodiments of the present disclosure;

FIG. 5A depicts a 2-D target in accordance with embodiments of thepresent disclosure;

FIG. 5B depicts 2-D targets in a point cloud in accordance withembodiments of the present disclosure;

FIG. 5C depicts a centroid of a 2-D target in point cloud data inaccordance with embodiments of the present disclosure;

FIG. 6 depicts a monitoring system in accordance with embodiments of thepresent disclosure;

FIGS. 7A-7B are block diagrams depicting functional components ofmonitoring systems in accordance with embodiments of the presentdisclosure;

FIG. 8 is a block diagram depicting a monitoring and control stationprovided as part of a monitoring system in accordance with embodimentsof the present disclosure;

FIG. 9 is a flowchart depicting aspects of a process for detectingmovement of an underwater structure in accordance with embodiments ofthe present disclosure;

FIG. 10 depicts a user interface presented in connection with theoperation of a system in accordance with embodiments of the presentdisclosure;

FIG. 11 depicts a point selection operating mode in connection with theuser interface of FIG. 10;

FIG. 12 depicts an area selection operating mode in connection with theuser interface of FIG. 10;

FIG. 13 is a flowchart depicting aspects of a process for detectingvibration of an underwater structure in accordance with embodiments ofthe present disclosure;

FIG. 14 depicts the selection of control points and the measurement ofunderwater structure vibration and vibration modes in accordance withembodiments of the present disclosure;

FIG. 15 depicts exemplary data obtained by a monitoring system inaccordance with embodiments of the present disclosure;

FIG. 16 depicts a Fourier transform of the data obtained by a monitoringsystem in accordance with embodiments of the present disclosure depictedin FIG. 15;

FIG. 17 is a flowchart depicting aspects of a process for the detectionof the temperature of an underwater structure in accordance withembodiments of the present disclosure;

FIG. 18 is a flowchart depicting aspects of a process for the detectionof leaks from an underwater structure in accordance with embodiments ofthe present disclosure;

FIG. 19 illustrates an example of sea floor deformation due to welloverpressure; and

FIG. 20 depicts a structure in accordance with embodiments of thepresent disclosure for subsidence and movement detection.

DETAILED DESCRIPTION

FIG. 1 depicts an example drilling and production system 100, thecomponents of which can be monitored using systems and methods inaccordance with embodiments of the present disclosure. The system 100can include, for example and without limitation, processing platforms104, jack-up platforms 108, floating platforms 112, pipelay vessels 116,pipelines 120, risers 124, manifolds 128, wells 130, touch down point135, suction piles or anchors 136, chain 137, slip joints 138 andblowout preventers 132. The various components of the system 100 aresubject to vibrations or other movements, temperature variations, andleaks, which can all be indications of internal issues with the system,the detection of some or all of which can be performed by embodiments ofthe present disclosure.

FIG. 2 depicts exemplary components 204, hereinafter referred to asunderwater features or structures 204, within a system 100 that can bemonitored by embodiments of the present disclosure. In this example, theunderwater structures 204 include wells 130 and associated blowoutpreventers 132, pipelines 120, and a manifold 128. FIG. 3 depicts ascene that includes the components shown in FIG. 2, and in additionincludes monitoring systems 304, mounted or applied targets, includingmounted three-dimensional (3-D) spherical target structures 308 andapplied two-dimensional (2-D) targets 312, and monuments 316, inaccordance with various embodiments of the present disclosure. Themonitoring systems 304 can comprise a lidar or other light-based 3-Dsensor or metrology system, and can be mounted to stationary structuresor platforms 320, can be placed directly on the sea floor, or can bemounted to an underwater vehicle 324, such as a remotely operatedvehicle (ROV) or to an autonomous underwater vehicle (AUV).

As can be appreciated by one of skill in the art, a monitoring system304 mounted to a stationary platform or structure 320 has an inherentconical field of regard 328. By incorporating a pan and tilt head in themonitoring system 304, the field of regard can be increased to a full360°, or even to over a hemisphere field of regard. As can further beappreciated by one of skill in the art after consideration of thepresent disclosure, a monitoring system 304 mounted to a movableplatform or vehicle 324 can be scanned, to obtain data in a push broomor flash camera fashion while the vehicle 324 moves to obtain data oflarge areas, or, for example where the vehicle is held stationary forsome period of time, from within a conical field of regard. The fieldsof regard of the monitoring systems 304 are depicted in the figure asareas 328. Accordingly, it can be appreciated that a single monitoringsystem 304 in accordance with embodiments of the present disclosure canbe positioned such that multiple components within a system 100 arewithin the field of regard 328 of the monitoring system 304. Moreover,components of the system 100 can be within the fields of regard 328 ofmultiple monitoring systems 304. As can be appreciated by one of skillin the art after consideration of the present disclosure, a monitoringsystem 304 can be operated to generate point cloud data, also referredto herein as simply a point cloud, which typically includes azimuthangle, elevation angle, intensity, and range information for a largenumber of points within a three-dimensional volume comprising a scene.

In accordance with embodiments of the present disclosure,three-dimensional 308 and/or two-dimensional 312 targets can be fixed tocomponents within the system 100. These targets 308, 312 arespecifically designed to provide control points within an image orwithin 3-D point cloud data produced by a monitoring system 304. FIG. 4Aillustrates a three-dimensional target 308, and FIG. 4B depicts thethree-dimensional target 308 within a point cloud 404 generated by amonitoring system 304. There are enough three-dimensional points in thepoint cloud data obtained by returns from target 308 to derive a centralpoint or centroid 408 with a high degree of accuracy, usually within 1-2mm. The 3-D targets 308 may be mounted to a structure 204.Omni-directional 3-D targets that are used topside are usually made ofplastic. Three-dimensional targets 308 in accordance with embodiments ofthe present disclosure can be specially configured to work in the deepocean so they hold their dimensions under extreme pressure and areresistant to corrosion. In accordance with further embodiments of thepresent disclosure, the 3-D targets 308 feature a Lambertian reflection.FIG. 5A shows a two-dimensional target 312, FIG. 5B depicts the 2-Dtarget 312 within a point cloud 504, and FIG. 5C depicts a centroid 508of the 2-D target 312 in point could data. These targets 312 can bepainted or otherwise applied to a structure.

In accordance with some embodiments of the present disclosure,three-dimensional 308 and/or two dimensional 312 targets can be fixed tomonuments 316 or upon any other structure, for example, pipelines 120,risers 124, manifolds 128, wells 130, touch down point 135, anchors,suction piles, pin piles, blowout preventers 132, or other components orexamples of underwater structures 204. As can be appreciated by one ofskill in the art after consideration of the present disclosure, theinclusion of targets 308 and 312 facilitates the reliable and repeatablemonitoring of a specific location on a monitored component or structure204 within a system 100, promoting the accuracy of measurements taken bythe monitoring systems 304. This is through the highly accurate derivedcontrol points allowed by these designed targets 308, 312. As can alsobe appreciated by one of skill in the art after consideration of thepresent disclosure, measurements taken by one or more monitoring systems304 can be compared to highly accurate top-side survey data of anindividual component, known as dimensional control data. Moreover, byincluding monuments 316 and associated targets 308 and 312, the locationof a system 100 component, or location on a component, at a particularpoint in time, can be determined with high accuracy (e.g., less than 1cm). This is extremely useful for typical subsea field issues such assubsidence, well growth, linear or rotational movement, or scour. Inaccordance with still other embodiments of the present disclosure, theinclusion of a three-dimensional 308 or a two-dimensional 312 target isnot required. Accordingly, the monitoring of legacy components within asystem 100 that do not include such indicia 308 or 312, including seabedfeatures themselves, is possible.

FIG. 6 depicts a monitoring system 304, mounted to a supportingstructure 320, in accordance with at least some embodiments of thepresent disclosure. The monitoring system 304 generally includes one ormore lidar devices 600 that can be pointed along a selected line ofsight via a pan and tilt head 604 that connects the lidar device 600 tothe supporting structure 320. Alternatively or in addition to a lidardevice 600, a monitoring system 304 can include other optical metrologysystems. The supporting structure 320 can comprise a frame 624 that isin turn mounted to a stationary pad, a mud mat, another structure on theseabed, or placed directly on the seabed. In accordance with otherembodiments of the present disclosure, the frame 624 may be carried by avehicle, such as an ROV. In accordance with still other embodiments ofthe present disclosure, a monitoring system 304 can be mounted to avehicle via a pan and tilt head 604 or can be mounted directly to avehicle.

In at least some embodiments of the present disclosure, the monitoringsystem 304 can itself comprise a subsea system with a platform withnumerous selectable functions. The frame 624 can be designed to belowered by a crane from the surface vessel or rig or can be designed tobe deployed via an ROV. The frame 624 can be lowered using a crane lift628. The lift 628 is on a hinge so it lowers after deployment. Thisallows the lift 628 to drop out of the field of view of the lidardevices 600. The frame 624 can also include ROV manipulator handles 632to facilitate positioning the frame 624 using an ROV or AUV. Forexample, the frame 624 can be placed on a monument 316 or otherstructure. The bottom of the frame 624 can have a pin or receptacle, soit can be precisely lowered onto a mating receptacle or pin on astructure to enable precise location and alignment.

The support structure or frame 624 holds one or more lidar devices 600.Multiple lidars can be precisely located on the single structure so theycreate a single referenced point cloud. The lidar devices 600 can bemounted on pan/tilt units 604 to enable up to hemispherical coverage.Cameras and lights 636 can be mounted on the support structure 620 orthe pan/tilt units 604 to enable visual inspection along with the lidardata. A hot stab 640 can be included which enables the monitoring system304 to connect to the local infrastructure for power and orcommunications. The monitoring system 304 can further include one ormore non-optical point sensors, such as a conductivity, temperature, anddepth (CTD) device 642. Alternately or in addition, batteries and apower control system 644 can be included which allow for long-termautonomous deployment. The monitoring system 304 can also provideadditional capabilities including, but not limited to, data storage andbackup, vibration sensors, turbidity sensors, various chemical sensors,and communication devices. The monitoring system 304 can also providetiming signals (if needed) between multiple sensors to time-synchronizethe data collection of multiple sensors, such as from multiple lidardevices 600 and/or cameras 636. The communication devices can includeRF, optical, or acoustic devices. The communication devices cancommunicate with ROVs, AUVs, resident vehicles, other intelligentstructures in the field, or systems on the surface. The monitoringsystem 304 can store data, compress and send out samples, or autoprocess for change detection, and can send alarms or other indicationswhen change is detected. A single monitoring system 304 can providepower, data storage, and communications for other monitoring systems 304or lidar devices 600, to support multiple monitoring points around thesubsea equipment thereby allowing monitoring of underwater structures204 from different angles.

An acoustic compatt 648 can be included which enables the monitoringsystem 304 to be geo-spatially located using an acoustic positioningsystem. These can include Ultra-Short Baseline (USBL), Long Baseline(LBL) or other acoustic positioning systems. 2-D targets 312 can bemounted to the frame 624 or other components of the monitoring system,and 3-D targets 308 can be mounted to the frame 624 or other componentsof the monitoring system 304, to facilitate precisely locating themonitoring system 304 within a field via another stationary or movingmonitoring system 304 or lidar device 600.

FIGS. 7A and 7B are block diagrams depicting components of monitoringsystems 304 that may be contained within an underwater pressure vessel700 or co-located with one another in accordance with embodiments of thepresent disclosure. The monitoring systems 304 of FIGS. 7A and 7B differfrom one another in that the embodiment of the monitoring system 304 aillustrated in FIG. 7A includes a temperature measuring sub-system 702 athat compares a ratio of Raman wavelength amplitudes within a returnsignal to measure temperature, while the monitoring system 304 billustrated in FIG. 7B includes a temperature measuring sub-system 702 bthat calculates a ratio of light in the return signal based uponpolarization to measure temperature. Otherwise, the monitoring systems304 a and 304 b generally share components in common and can perform thesame types of measurements. Accordingly, except where noted, thefollowing description applies to both the embodiment of FIG. 7A and theembodiment of FIG. 7B.

The monitoring system 304 in accordance with embodiments of the presentdisclosure includes a lidar device 600 or other optical metrologysystem. As can be appreciated by one of skill in the art, a lidar device600 is an active optical system that operates by transmitting lighttowards a target, receiving reflected light from the target, anddetermining the range to the target based upon time of flightinformation determined from the amount of time elapsed between thetransmission of light from the light source and the time at which thereflected light or return signal is received at the receiver. As usedherein, a target can include an area or feature on an underwaterstructure 204, including manmade structures and natural features orstructures, 3-D targets 308 mounted to an underwater structure 204, and2-D targets 312 applied to an underwater structure 204. In addition, thelocation of a point on the target from which light is reflected can belocated relative to the lidar device 600 in three-dimensional space bycombining the range information with the known azimuth and elevationinformation via scanner location (e.g. as an azimuth angle and anelevation angle) for scanning lidar devices 600, pixel location formulti-pixel lidar devices 600, or a combination of the two. The fourthdimension, time, is also recorded so measurements and features can becompared over time.

The components of the monitoring system 304 thus include a light source704. The light produced by the light source 704 can be collimated orvariably focused by optics 708. In accordance with at least someembodiments of the present disclosure, the light source 704 is a pulsedbeam laser. As can be appreciated by one of skill in the art afterconsideration of the present disclosure, the light source 704 canproduce light having a selected wavelength or range of wavelengths. Asan example, but without limitation, the light source 704 may comprise ablue-green laser light source. As a further example, the light source704 may have an output centered at 532 nm. Other wavelengths can also beused, for example to optimize performance in response to various waterconditions. In accordance with still other embodiments, the light source704 may produce non-collimated light. In accordance with still otherembodiments, the light source 704 may be light emitting diode (LED)based, continuous wave (CW) laser based, modulated CW based, structuredlight, or some other light source.

The variable focus optics 708 can include traditional mechanicalfocusing elements, or non-mechanical elements, such as may be providedby fluid lenses, liquid crystal devices, electro-optic devices, andother optical elements. The ability to focus the beam can be used tooptimize signal return for a specific target at a specific range forspecific water conditions. The light can then be adjusted in magnitudeby a variable filter or attenuator 712. This is advantageous forunderwater sensing as the attenuation of seawater or other water bodiescan vary dramatically, thus dramatically changing the return signal,which can strain the dynamic range of the receiver. One method forreducing the required dynamic range of the receiver is to adjust thelight output power from the transmitter. This can be achieved by thevariable attenuator 712. As examples, the variable attenuator 712 caninclude standard neutral density filters, other attenuation filters, orpolarization elements.

The optical train can also include a variable polarization rotator 716.It is known that the polarization of the transmitted light can affectthe backscatter power, which is a source of noise at the lidar device600 receiver. Transmission range can therefore be optimized by adjustingthe polarization rotation of the output light. In the monitoring system304 a of FIG. 7A, in which a ratio of the amplitude of differentselected wavelengths within a return signal is used to measuretemperature, the variable polarization rotator 716 can impart anypolarization to the output light. In the monitoring system 304 b of FIG.7B, the variable polarization rotator 716, if included, can provideeither a left hand circular or right hand circular polarization (incombination with quarter wave plate 762), as some type of circularpolarization is needed in order to compare polarization ratios in areturn signal for temperature measurement in that embodiment.

Transmit and receive (Tx/Rx) optics 720 are used to make the sensormonostatic. Monostatic sensors have the distinct advantage of simplifiedscanning as the transmitter and receiver are pointed at the samelocation with the same scanning mechanism, resulting in calibration andreliability performance that is superior to bistatic systems. A scanningdevice 724 can then be used to accurately direct the transmitted beamand the field of view of the receiver simultaneously to a scene througha window 728 in the enclosure 700. The scanning device 724 can include asteering mirror or other beam steering device, such as amicro-electro-mechanical system (MEMs), liquid crystal, acousto-optic,or electro-optic device, for precise control of the pointing of thelight source and receiver toward a target, such as an underwaterstructure 204, and at known angles relative to the monitoring system304.

Light reflected from the target is received by the scanning device 724and is split by a beam splitter element included in the Tx/Rx optics720. Light from the Tx/Rx optics 720 is provided to a receive telescope730, which is configured to focus the received light so that it can beimaged onto the sensor elements of various receivers 744, 756, and/or760 included in the monitoring system 304. In the monitoring system 304a that includes a wavelength based temperature measuring sub-system 702a, a variable polarization rotator 732 can be used to optimize thesignal-to-noise ratio (SNR) of the return signal by selecting theoptimal polarization for the hard target return. In the monitoringsystem 304 b that includes a polarization based temperature measuringsub-system 702 b, the variable polarization rotator 732 is omitted.

A fast shutter 736 is provided to block any stray light from the primarybeam as it exits the window 728, after being directed by the scanningdevice 724. The fast shutter 736 is timed with high speed electronics,which may be implemented by a processor 748, to block the window 728reflection from a transmitted pulse and then open quickly to capturereturns from close targets. A beam splitter 740 splits off a portion ofthe return signal and directs it to the primary receiver 744. The beamsplitter 740 may be in the form of a chromatic or achromatic beamsplitter. For example, the beam splitter 740 may comprise a chromaticbeam splitter that provides light at the primary wavelength output bythe light source to the primary receiver 744, and that provides theremaining light to the temperature measuring sub-system 702. The primaryreceiver 744 is used for the range, vibration, and leak detectionmeasurements made by the lidar system 600. The primary receiver 744includes an optical sensor or detector, such as a photodiode, anavalanche photodiode, a photomultiplier tube, a silicon photomultipliertube, a Geiger mode avalanche photodiode, charge coupled device (CCD)detector, complementary metal oxide semiconductor (CMOS) detector, orother optical detector. It can also include an electronic amplifierand/or thermal control elements and circuitry. In addition, the primaryreceiver 744 can include or be associated with a narrow band filter toreduce background light. A focusing optic 746 can be included to focuslight from the beam splitter 740 onto the sensor of the primary receiver744. In accordance with embodiments of the present disclosure, theprimary receiver 744 may comprise a single or multiple pixel sensor.Information regarding the range to the target is monitored by aprocessor 748, which controls and/or has access to information regardingthe time at which transmitted light is output, and the time at which areturn signal, comprising transmitted light that has been reflected froma target, is received by the primary receiver 744. In addition,information from the scanning device 724, from a pan and tilt head 604,and/or the location of a receiving pixel in a lidar device 600 or camera636 having a multiple pixel sensor can be used by the processor 748 todetermine the azimuth angle and elevation angle to the target. Thisinformation can then be combined with timing information, and inparticular the time at which the transmitted pulse of light produced bythe light source 704 is sent towards the target, and the time that thereturn signal is received at the primary receiver 744. The rangemeasurement determined from the timing information can then be appliedto obtain a location of the target relative to the monitoring system304. As can be appreciated by one of skill in the art afterconsideration of the present disclosure, the primary receiver 744 alsoprovides information regarding the intensity of the return signal, whichcan be analyzed in connection with determining, for example, whether thereturn is from an underwater structure 204, water, or a plume of fluid.Moreover, the intensity may be provided from the sensor as a voltagesignal.

The processor 748 can include any processor capable of performing orexecuting instructions encoded in system software or firmware 763 storedin data storage or memory 764, such as a general purpose programmableprocessor, controller, Application Specific Integrated Circuit (ASIC),Field Programmable Gate Array (FPGA), or the like. Moreover, theexecution of that software or firmware 763 can control the operation ofthe lidar system 600, including the acquisition of point cloud data thatincludes azimuth angle, elevation angle, intensity, and rangeinformation taken from an underwater scene. The execution of thesoftware 763 by the processor 748 can be performed in conjunction withthe memory 764, including the short or long-term storage of timinginformation, range information, point cloud data generated by themonitoring system 304, control point locations, or other controlinformation or generated data. The memory 764 can comprise a solid-statememory, hard disk drive, a combination of memory devices, or the like.The monitoring system 304 can additionally include various sensors. Forexample, the monitoring system 304 can include a CTD device 642 formeasuring the conductivity (and thus the salinity), the temperature, andthe depth of the water at the location of the monitoring system 304.Because a CTD device 642 must be in direct contact with the surroundingwater, it can be mounted outside of or adjacent an aperture in theenclosure 700.

As has been described in U.S. Pat. No. 4,123,160, the Raman return fromwater molecules can be used to determine the temperature of the water.Typically, this requires a full spectrometer to analyze the spectrum ofthe Raman return. In accordance with embodiments of the presentdisclosure, temperature measurements are performed by comparing twospectral channels or two polarization channels. Either of theseapproaches are allowed by a monitoring system 304 in accordance withembodiments of the present disclosure that incorporates a temperaturemeasuring sub-system 702 a or 702 b, as described herein.

Moreover, the temperature measurement subsystem 702 can measure thetemperature of water at a distance from the monitoring system 304. Thetemperature measurement subsystem generally includes a beam splitter 750or 752 that divides the signal received from the primary beam splitter740 into a first channel provided to a first temperature channelreceiver 756 and a second channel that is provided to a secondtemperature channel receiver 760. First 774 and second 776 focusingoptics can be included to focus light from the beam splitter 750 ontothe respective temperature channel receivers 756 and 760.

In a monitoring system 304 a that includes a temperature measurementsub-system 702 a that uses different wavelengths for temperaturemeasurement (see FIG. 7A), the beam splitter 750 used to divide thereturn signal into two channels may comprise a chromatic or anachromatic beam splitter. A first one of the channels is passed througha first narrowband filter 754 before being provided to a firsttemperature channel receiver 756. A second one of the channels is passedthrough a second narrowband filter 758 before being provided to a secondtemperature channel receiver 760. The passband of the first narrowbandfilter 754 is selected to encompass a first Raman wavelength, while thepassband of the second narrowband filter 758 is selected to encompass asecond Raman wavelength. For example, where the transmitted light fromthe light source 704 has a wavelength of 532 nm, the first passband canbe about 10 nm wide and can be centered at a wavelength of about 640 nm,and the second passband can be about 10 nm wide and can be centered at awavelength of about 655 nm, where “about” is +/−10% of the stated value.The temperature channel receivers 756 and 760 are optical detectors. Thetemperature channel receivers 756 and 760 can thus include a photodiode,CCD detector, CMOS detector, an avalanche photodiode, a photomultipliertube, a silicon photomultiplier tube, a Geiger mode avalanchephotodiode, or other optical detector. As a further example, thetemperature channel receivers 756 and 760 can comprise single element orpixel sensors. The temperature channel receivers 756 and 760 can alsoinclude an electronic amplifier, thermal control elements and circuitry,focusing optics, or other components. As can be appreciated by one ofskill in the art after consideration of the present disclosure, theratio of the amplitude of the signal comprising the first Ramanwavelength detected at the first temperature channel receiver 756 to theamplitude of the signal comprising the second Raman wavelength detectedat the second temperature channel receiver 760 gives the temperature ofthe water at a selected range and angular location.

In a monitoring system 304 b that includes a temperature measurementsub-system 702 b that measures a ratio of differently polarized lightfor temperature measurement (see FIG. 7B), linearly polarized light fromthe light source 704 is passed through a first quarter wave plate 762,which can be located before or after the scanning device 724, to producea circularly polarized output beam. A second quarter wave plate 766converts circularly polarized light in the return signal to linearlypolarized components. If the target reflection reverses the circularpolarization, then a second quarter wave plate 766 is not needed. Apolarization beam splitter 752 then divides the portion of the returnsignal received from the primary beam splitter 740 into two channelsaccording to the polarization of the received light. A first one of thechannels, comprising light of a first polarization (e.g. verticallypolarized light), is provided to a first temperature channel receiver756. A second one of the channels, comprising light of a secondpolarization (e.g. horizontally polarized light), that is opposite thepolarization of the light in the first channel, is provided to a secondtemperature channel receiver 760. The temperature channel receivers 756and 760 are optical detectors that receive one of the oppositelypolarized signals. The temperature channel receivers 756 and 760 canthus include a photodiode, CCD detector, CMOS detector, an avalanchephotodiode, a photomultiplier tube, a silicon photomultiplier tube, aGeiger mode avalanche photodiode, or other optical detector. As afurther example, the temperature channel receivers 756 and 760 cancomprise single element or pixel sensors. The temperature channelreceivers 756 and 760 can also include an electronic amplifier, thermalcontrol elements and circuitry, focusing optics, or other components. Ascan be appreciated by one of skill in the art after consideration of thepresent disclosure, the ratio of the amplitude of the signal from thelight of the first polarization detected at the first temperaturechannel receiver 756 to the amplitude of the signal from the light ofthe second, opposite polarization detected at the second temperaturechannel receiver 760 gives the temperature of the water at a selectedrange and angular location.

A key advantage of a monitoring system 304 architecture in accordancewith embodiments of the present disclosure is that the range and anglefrom the lidar device 600 of the monitoring system 304 to the target areknown, so the thermal measurement can be optimized at particular pointsin space, thus improving the SNR for the thermal measurement andtargeting the exact location of interest. For example, when the location(angle, angle, and range) of a pipe joint relative to the monitoringsystem 304 is known exactly, then a location within the water volumeimmediately adjacent (e.g. above) that exact location can be selectedfor the temperature measurement by pointing a lidar system 600 at thelocation. Furthermore, the return signal can be gated to only receivesignal from a range corresponding to the selected location within thewater, as opposed to the entire water path, thus improving the signal tonoise ratio. This is not included in the prior art for thermalmeasurements. As another advantage, embodiments of the presentdisclosure provide for simultaneous or near simultaneous monitoring ofmovement and temperature of an underwater structure 204 using a singlemonitoring system 304.

As can be appreciated by one of skill in the art after consideration ofthe present disclosure, the basic components of the lidar system 600 arethe light source 704 and the primary receiver 744. Embodiments of thepresent disclosure can include all of the components illustrated inFIGS. 7A and 7B, additional or alternate components, or a subset ofthese components. In accordance with embodiments of the presentdisclosure, the range and angle measurements should all be compensatedusing techniques described in U.S. Pat. Nos. 8,184,276 and 8,467,044.The memory 764 can be used for storing the location information,operating instructions, generated data, and the like. An input/output orcommunication interface 768 can be included for transmitting determinedinformation to a monitoring and control station 804 (see FIG. 8) orother system or control center in real-time, near real-time, orasynchronously. A power source and distribution bus 772 can also beintegrated with the monitoring system 304. Various elements of amonitoring system 304 as disclosed herein can be provided as or bydiscrete or integrated components. For example, the various receivers744, 756, and 760 can be implemented as photo-sensitive detectors formedin the same semiconductor substrate. Moreover, optical elements, such asbeam splitters 740, 750, and or 752 can be formed on a substrate that isbonded to the semiconductor substrate in which the photo-sensitivedetectors are formed, creating an integrated chip or package.

FIG. 8 is a block diagram depicting human interface and other componentsincluded in a monitoring and control station 804 that can be provided aspart of or in conjunction with a subsea monitoring system 304 inaccordance with embodiments of the present disclosure. The monitoringand control station 804 can be provided as a top-side facility, carriedby a mobile platform, such as a surface ship or a submersible vehicle,mounted to a fixed or stationary platform, such as a productionplatform, or located at an on-shore facility. The monitoring and controlstation 804 facilitates or performs functions that include providingoutput to and receiving input from a user or from an automatedprocessing center. The monitoring and control station 804 generallyincludes a processor 808 and memory 812. In addition, the monitoring andcontrol station 804 can include one or more user input devices 816 andone or more user output devices 820. The monitoring and control station804 also generally includes data storage 824. In addition, acommunication interface 828 can be provided, to support interconnectionof the monitoring and control station 804 to the underwater componentsof the monitoring system 304, and/or to other systems. This interfacecan be used as a command and control interface of 804 to anotherautonomous device that provides the inputs and reads outputs thatreplaces human user interfaces 816 and 820.

The processor 808 may include a general purpose programmable processoror any other processor capable of performing or executing instructionsencoded in software or firmware. In accordance with other embodiments ofthe present disclosure, the processor 808 may comprise a controller,FPGA, or ASIC capable of performing instructions encoded in logiccircuits. The memory 812 may be used to store programs and/or data, forexample in connection with the execution of code or instructions by theprocessor 808. As examples, the memory 812 may comprise RAM, SDRAM, orother solid-state memory. In general, a user input device 816 isincluded as part of the monitoring and control station 804 that allows auser to input commands, including commands that are transmitted to theunderwater components of the monitoring system 304, to control thatsystem 304. Examples of user input devices 816 that can be provided aspart of the monitoring and control station 804 include a keyboard,keypad, microphone, biometric input device, touch screen, joy stick,mouse, or other position encoding device, or the like. A user outputdevice 820 can, for example, include a display, speaker, indicator lamp,or the like. Moreover, a user input device 816 and a user output device820 can be integrated, for example through a graphical user interfacewith a pointing device controlled cursor or a touchscreen display. Likethe memory 812, the data storage 824 may comprise a solid-state device.Alternatively or in addition, the data storage 824 may comprise, but isnot limited to, a hard disk drive, a tape drive, or other addressablestorage device or set of devices. Moreover, the data storage 824 can beprovided as an integral component of the monitoring and control station804, or as an interconnected data storage device or system.

The data storage 824 may provide storage for a subsea monitoring systemapplication 832 that operates to present a graphical user interfacethrough the user output device 820, and that presents point cloud data,or data derived from point cloud data, obtained by one or moreunderwater monitoring systems 304. The application 832 can furtheroperate to receive control commands from a user through the user inputdevice 816, including commands selecting targets or other control pointson an underwater structure 204. In accordance with embodiments of thepresent disclosure, the application 832 can perform various functionsautonomously, such as identifying underwater structures 204, identifyingfeatures on underwater structures 204, identifying a centroid of anunderwater structure 204 or a feature of an underwater structure 204,identifying control points on underwater structures 204, identifyingtarget centroids, monitoring the motion, vibration, and/or temperatureparameters of underwater structures 204, or other operations. Suchautomated operations can be implemented using, for example, imagerecognition techniques. The data storage 824 can additionally providestorage for the selected control points 836, for point cloud data 840generated by operation of one or more monitoring systems 304, and forrange, vibration, vibration mode, temperature, leak detection, or othermeasurements or data generated by a monitoring system 304. In accordancewith still other embodiments of the present disclosure, the systemapplication 832 can be executed to detect motion, vibration, vibrationmode, temperature, changes, features, lack of features, other anomalies,or leaks instead of or in conjunction with execution of the systemsoftware 763 by the processor 748 of the monitoring system 304. The datastorage 824 can also store operating system software 844, and otherapplications or data.

FIG. 9 is a flowchart depicting aspects of a process in accordance withembodiments of the present disclosure for the detection of movement ofan underwater structure 204. As a first step, an initial scan of anunderwater scene is taken (step 904). In accordance with embodiments ofthe present disclosure, the initial scan is a three-dimensional scanobtained using one or more monitoring systems 304. In particular, and ascan be appreciated by one of skill in the art after consideration of thepresent disclosure, taking a scan of an underwater scene includesoperating a light source 704 to illuminate the scene, and receiving areturn signal reflected from objects in the scene that is provided to aprimary receiver 744. The initial scan can be a relativelylow-resolution scan. In particular, only enough detail to determinewhether a desired underwater structure 204 or portion of an underwaterstructure 204 is within the field of regard 328 of the monitoring system304 is required. In general, the accuracy of a scan, includingrelatively low or relatively high-resolution scans, is greatest when themonitoring system 304 is statically mounted to a stationary platform. Asa next level of accuracy, the monitoring system 304 can operate to scana scene while it is mounted to a mobile platform or vehicle, such as anAUV/ROV, while that platform or vehicle is stationary on the seabed orsome other structure. As a less accurate technique, but one that canstill be viable, the monitoring system 304 can perform a scan whilemounted to a floating or moving mobile platform or vehicle, such as anAUV/ROV.

At step 908, a determination is made as to whether the underwaterstructure 204 of interest is included in the point cloud data obtainedfrom the scene. In accordance with embodiments of the present disclosurethis determination can be made in connection with presenting the imagederived from the point cloud data to a user through a user output device820 included as part of a monitoring and control station 804 inoperative communication with the monitoring system 304. An example of auser interface 1004 presented to a user by a user output device 820 isdepicted in FIG. 10. As shown, the user interface 1004 can include auser input section 1008 containing a variety of data entry fields andvirtual buttons that can be utilized by a user to enter controlinstructions or data through manipulation of one or more user inputdevices 816. The user interface 1004 can additionally present an imageof the underwater scene 1012 generated from the point cloud dataobtained by the initial scan of the scene. The image can include pointcloud data obtained from a single lidar device 600, or that has beenstitched together from multiple lidar devices 600. Moreover, data can beobtained from lidar devices 600 or other optical devices included indifferent monitoring systems 304. Verification that the intendedunderwater structure 204 or portion of an underwater structure 204 iswithin the field of view of the monitoring system 304 can thus involve amanual operation, in which a user or operator makes such a determinationby viewing the presented image 1012. As an alternative, thedetermination as to whether the intended underwater structure 204 isincluded in the scene can be performed through automated processes, suchas through the execution of image recognition software included in orprovided separately from the system application 832. If it is determinedthat the underwater structure 204 is not included in the point clouddata obtained, the field of view of the monitoring system 304 can bechanged (step 912). Changing the field of view of the monitoring system304 can include adjusting the field of regard of one or more lidarsystems 600 via an associated pan and tilt head 604, through operationof the monitoring system 304 scanning device 724, or throughrepositioning the monitoring system 304 itself. In accordance with atleast some embodiments of the present disclosure, changing the field ofview of a lidar system 600 can be performed in response to controlling apan and tilt head 604 or other mechanism while the current field of viewis displayed to the user through the user output device 820 in real timeor near real-time.

After determining that the desired underwater structure 204 is withinthe imaged scene, a high resolution scan of the scene can be taken usingthe monitoring system 304 (step 916). The high resolution scan can be ofan area within the initial scan that has been selected by a user througha user input device 816 provided as part of the monitoring and controlstation 804 in communication with the monitoring system in 304. One ormore control points 1104 (see FIG. 11) can then be selected formonitoring, and information regarding the location of the selectedcontrol points 1104 in three-dimensional space can be stored in the datastorage 824, memory 812, and/or memory 764 (step 920). The selection ofthe control points 1104 can be made through the interaction of a userwith the monitoring system 304 via the user interface 1004. For example,the user can manipulate a cursor to select the locations of controlpoints 1104 on a visualization of a 3-D scan of an underwater structure204 presented to the user by the user output device 820 as an image 1012using a pointing device provided as or part of a user input device 816in a point and click operation. The control points 1104 can correspondto unique features on the underwater structure 204, the centroid oflidar targets 308 or 312, the centroid of the underwater structure, thecentroid of selected areas of the underwater structure 204, or the like.In accordance with still other embodiments of the present disclosure,the control points 1104 can be selected through an automated processthat identifies the centroid of the underwater structure 204, thecentroid of features or components of the underwater structure 204, theedges of structural features, the centroid of mounted 3-D 308 or applied2-D 312 targets, or points at a selected interval along an underwaterstructure 204. An automated process for selecting control points 1104can operate in combination with a manual process, where a user selectsan area or feature, and the automated process determines the preciselocation for the control points 1104. For instance, a user can select atarget 308 or 312 or feature on an underwater structure 204, and theautomated process can identify the centroid of the target or feature foruse as the control point 1104 location. These control points 1104 canthen be used as reference points for monitoring various parameters ofthe underwater structure 204, including but not limited to a shift in alocation of the underwater structure 204.

In accordance with further embodiments of the present disclosure, theselection of control points 1104 can comprise the selection of an areaof interest 1204 of an underwater structure 204 by a user throughinteraction with the user interface 1004 presented by execution of theapplication software 832 by the processor 808, the user input device816, and the user output device 820. (see FIG. 12). The 3-D point clouddata from within the selected area of interest 1204 or a sampling ofthat data can then be stored as a reference surface, the location ofwhich can be monitored. Moreover, specific locations within a selectedarea of interest can be identified by an automated process for use ascontrol points. For instance, the centroid of a component of theunderwater structure 204 within the selected area, the centroid of atarget 308 or 312, or the edge of a feature within the selected area canbe identified by the automated process and used as the location ofcontrol points, or control points can be defined by the automatedprocess at intervals along a surface within the selected area. Thelocation information from each of the selected control points can bestored as location points in 3-D space. The location can be an absolutelocation, or a location relative to a survey monument or other knownlocation. For example, the location can be relative to the location ofthe monitoring system 304, and/or to one or more reference points thatcan be located by the monitoring system 304, such targets 308 or 312provided on a monument 316 or on another underwater structure 204 withinthe field of view of the monitoring system 304.

At step 924, a determination is made as to whether a selected time haselapsed. If the selected time has not elapsed, the process can idle atstep 924. In accordance with embodiments of the present disclosure, theselected time can be anywhere from a fraction of a second to seconds,minutes, hours, days, months, years, or any other time period. After ithas been determined that the selected time has elapsed, an additionalscan of the underwater structure 204 is taken using the monitoringsystem 304 (step 928). The locations of the selected control points 1104in the point cloud data from the first or previous high resolution scanof the underwater structure 204 that have been stored are then comparedto the locations of the selected control points 1104 in the point clouddata from the additional or subsequent high resolution scan of theunderwater structure 204 (step 932). Moreover, embodiments of thepresent disclosure can include comparing the relative locations of aselected, unique pattern of multiple points 1104 to ensure that the samestructural features are being compared between the different scans. Inaccordance with at least some embodiments of the present disclosure, thelocations of control points 1104 can be stored as absolute locations, orrelative to a monument 816, lidar system 304 location, other underseastructure 204, or the like.

If it is determined (step 936) that the locations of one or more of thecontrol points 1104 has changed, an indication that the underwaterstructure 204 has moved is generated (step 940). Alternatively, if it isdetermined (step 936) that the locations of the control points 1104 havenot changed, an indication that the underwater structure 204 has notmoved is generated (step 944). The indications of movement ornon-movement can be presented through a user interface 1004, provided asan output to another system, or stored.

A determination can next be made as to whether operation of themonitoring system 304 to detect movement of the underwater structure 204is to continue (step 948). If operation is to continue, the process canreturn to step 924. The monitoring system 304 can thus be operated toperiodically scan a scene to determine whether the location of one ormore underwater structures 204 associated with selected control points1104 has shifted or has otherwise moved. If a determination is made thatoperation is not to continue, the process can end.

FIG. 13 is a flowchart depicting aspects of a process in accordance withembodiments of the present disclosure for the detection of vibration ofan underwater structure 204. Initially, at steps 1304-1320, a processthat is the same as or similar to the process described in connectionwith FIG. 9 is performed. Accordingly, an initial scan of an underwaterscene is taken using a monitoring system 304 (step 1304), a manual orautonomous determination is made as to whether a desired underwaterstructure or portion of a structure 204 is within the scene (step 1308),and the field of view is changed if the desired underwater structure 204is not within the field of view (step 1312). A high resolution scan ofthe structure is then taken (step 1316), and a set of one or morecontrol points 1104 or 1404 (see FIG. 14) is identified and locationinformation regarding those control points 1104 or 1404 is stored indata storage 824 or memory 764 or 812 (step 1320). In a secondembodiment a high resolution scan is not needed in order to select thecontrol points for a vibration measurement. In accordance withembodiments of the present disclosure, the set of control points 1104 or1404 selected in connection with vibration monitoring of a particularunderwater structure 204 can be located at intervals along thatstructure 204 or a portion of the structure. For example, but withoutlimitation, a set of control points 1104 or 1404, may be defined alongan underwater structure 204 comprising a section of pipe 1408 (see FIG.14). As another example, control points 1104 can be selected across areference surface of a structure (see FIG. 11). Moreover, wherevibration monitoring is being performed concurrently with movementmonitoring, the same control points 1104 can be used by both processes.

At step 1324, multiple range measurements are taken along a line, whichmay be defined as an azimuth angle and an elevation angle relative tothe monitoring system 304 that intercepts a first one of the controlpoints 1104 or 1404, at least at the time the location of the firstcontrol point 1404 was defined. In general, the set of multiple rangemeasurements contains at least three such measurements, but usually tensto hundreds are taken. In one embodiment the time interval for themeasurements is variable and can be selected. In another embodiment thetime interval is fixed. The multiple range measurements are time stampedand stored.

A determination can then be made as to whether a set of rangemeasurements for all of the control points 1104 or 1404 in the set ofcontrol points 1104 or 1404 have been obtained (step 1328). If not, afurther control point 1404 is selected (step 1332), and the processreturns to step 1324, at which multiple range measurements are takenalong a line to the original location of the further control point 1404.These additional range measurements are then time stamped at step 1328.The collection of multiple range measurements with respect to differentcontrol points 1104 or 1404 can continue for each control point 1404 inthe set. In accordance with embodiments of the present disclosure, themultiple range measurements for the different control points 1104 or1404 are completed within a relatively short time span, such that acoherent plot of a movement of the underwater structure 204 can beprovided from multiple range measurements for the different controlpoints 1104 or 1404.

At step 1336, the range measurement data within a set obtained for afirst control point 1404 is selected. The range measurements within thatset are then compared to one another (step 1340). The magnitude of anydifferences in measured range at different times, which corresponds tothe magnitude of motion of the underwater structure 204 along the linefrom the lidar device 600 to the original location of the control point1404 on the underwater structure 204 over the time interval betweenadjacent measurements, can then be calculated (step 1344). Moreover,such movement can be plotted over time, as shown in FIG. 15, and afrequency of vibration can be calculated from the frequency spectra, asshown in FIG. 16. In the example of FIGS. 15 and 16, the collected dataindicates a spectral peak, and thus a vibration of the underwaterstructure 204 at or near the selected control point, of 9.86 Hz. Adetermination is then made as to whether range measurement data for allof the control points 1104 or 1404 has been analyzed (step 1348). Ifrange measurement data for all of the control points 1104 or 1404 hasnot been analyzed, the process can return to step 1336, and measurementdata from a next control point can be collected. If range measurementdata for all of the control points 1104 or 1404 has been analyzed, anyvibration or other movement detected with respect to the individualcontrol points 1104 or 1404 can be compared to the other control points1104 or 1404, and a vibration mode of the underwater structure orportion of the underwater structure 204 associated with the controlpoints 1104 or 1404 can be calculated (step 1352). In accordance withembodiments of the present disclosure, a visualization of the pointcloud data of the structure, including the control points at whichcomparisons or other measurements are made, can be presented to a user,together with information regarding the frequency and magnitude of thevibration of the structure, through a user output device 820.

A determination can then be made as to whether the vibration monitoringprocess should continue (step 1356). If operation is to continue, theprocess can return to step 1332, and a control point (e.g. the firstselected control point) can be selected, and range measurements can betaken along a line corresponding to that control point 1404, at least atthe time that next control point 1404 was selected. Alternatively, theprocess can end.

As can be appreciated by one of skill in the art after consideration ofthe present disclosure, vibration monitoring of points on an underwaterstructure 204 can be performed with respect to a single control point1104 or 1404, or multiple control points 1104 or 1404. Moreover, wheremultiple control points 1104 or 1404 are monitored at about the sametime (e.g. sets of range measurements for control points 1104 or 1404within a set of control points 1104 or 1404 are taken sequentially),information regarding the mode of vibration along the underwaterstructure or portion of the underwater structure 204 associated with thecontrol points 1104 or 1404 can be obtained. In addition, the monitoringof an underwater structure 204 for movement can encompass monitoring theunderwater structure 204 for vibration. For instance, the average rangeobtained from a set of range measurements made to a selected controlpoint 1104 or 1404 can be compared to the range obtained from a set ofrange measurements made to that selected control point 1104 or 1404 atanother time to determine whether the associated structure 204 hasmoved. Accordingly, the processes of monitoring for movement andmonitoring for vibration using a lidar device 600 included in amonitoring system 304 in accordance with embodiments of the presentdisclosure can be performed simultaneously or nearly simultaneously(e.g. within several seconds of one another). Although the process formonitoring vibration has been described as including operations that areperformed in a particular sequence, it should be appreciated thatvarious operations can be performed simultaneously or in parallel. Forexample, determinations of whether control points have moved or arevibrating can be made while data regarding the range to those or othercontrol points is being generated. It is appreciated by one skilled inthe art that the vibration measurement is only in the direction parallelto the line of site of the monitoring device 304. Rapid movement in aperpendicular direction may not be captured by the range measurements,therefore a second monitor device 304 should monitor from aperpendicular direction, or the same monitoring device should be movedto make this measurement. In accordance with at least some embodimentsof the present disclosure, the range and angle measurements should allbe compensated using techniques described in U.S. Pat. Nos. 8,184,276and 8,467,044.

With reference now to FIG. 17, aspects of a process for the detection ofthe temperature of an underwater structure 204 in accordance withembodiments of the present disclosure are depicted. Initially, at steps1704-1720, a process that is the same as or similar to the processesdescribed in connection with FIGS. 9 and 13 is performed. Accordingly,an initial scan of an underwater scene is taken using a monitoringsystem 304 (step 1704), a manual or autonomous determination is made asto whether a desired underwater structure or portion of a structure 204is within the scene (step 1708), and the field of view is changed if thedesired underwater structure 204 is not within the field of view (step1712). A high-resolution scan of the structure is taken once it isdetermined that the underwater structure 204 is within the field of view(step 1716), and a control point or set of control points 1104 or 1404is identified, with location information regarding those control points1104 or 1404 being stored in data storage 824 or memory 764 or 812 (step1720). In a second embodiment a high resolution scan is not needed inorder to select the control points for a temperature measurement. Inaccordance with embodiments of the present disclosure, the control pointor set of control points used in connection with measuring thetemperature of an underwater structure 204 can be the same as thecontrol points used for movement or vibration monitoring. As anotherexample, the control points used for measuring temperature can belocated at intervals along the underwater structure 204. As yet anotherexample, the control points can be at a selected point or points on thestructure 204, for instance at locations where the temperature of thestructure 204 is representative of the temperature of the structuregenerally, or where temperature monitoring is particularly important.

At step 1724, a temperature measurement is taken at a location adjacentto a first one of the control points. In particular, because thetemperature monitoring sub-systems 702 of embodiments of the presentdisclosure utilize techniques that measure the temperature of water, thelidar device 600 of the monitoring system 304 is controlled to directtransmitted light towards and to receive a return signal from a volumeof water immediately above or next to the selected control point on theunderwater structure 204. Accordingly, the monitoring system 304 usesinformation on the azimuth angle, elevation angle, and range from thelidar device 600 to the control point, to determine the azimuth angle,elevation angle, and range at which to take the temperature measurement.For example, where a selected control point is located on an underwaterstructure 204 in the form of a pipe having a diameter of 250 mm, thelidar device 600 can be controlled so that a temperature measurement istaken from an azimuth angle that is the same as the azimuth angle to thecontrol point, the elevation angle is increased as compared to theelevation angle to the control point, such that the temperaturemeasurement point is between 5-25 mm above the underwater structure 204,and the range is the same as the range to the selected control point,plus 125 mm (i.e. half the diameter of the underwater structure 204 atthe control point). The signal returned to the lidar device 600 ispassed to the temperature channel receivers 756 and 760, which measurethe amplitudes of the different wavelengths for the wavelength basedtemperature measurement sub-system 702 a, or the amplitudes of the lightof opposite polarizations for the polarization based temperaturemeasurement sub-system 702 b. The ratio of the different signals is thenused to calculate the temperature of the water immediately adjacent theselected control point on the underwater structure 204, which can inturn be correlated to a temperature of the underwater structure 204itself. In another embodiment a fixed range is used for the temperaturecollection range. This can be useful for collecting data while mountedon a moving platform. The height of the platform where the monitoringsystem 304 is mounted can be fixed above a structure, for instance apipe, or the seabed. As the platform moves, the temperature is measuredat a constant range from the sensor, or alternately multiple ranges fromthe sensor.

A determination is then made as to whether a selected number oftemperature measurements relative to the selected control point havebeen made (step 1728). In general, a number of temperature measurementsfrom the same location are made and averaged, to increase the accuracyof the measurement. For example, but without limitation, 1000measurements can be made sequentially over a short period of time. Afterthe selected number of temperature measurements have been made, anaverage of the determined temperature values obtained from the number oftemperature measurements can be output to a user through an outputdevice 820, transmitted to another system, and/or stored (step 1732).

At step 1736, a determination can be made as to whether a temperature ofan underwater structure 204 adjacent other control points should bedetermined. If so, the process can select the next control point (step1740), and the process can return to step 1724. If it is determined atstep 1736 that no other control points 1104 or 1404 in a set remain fortemperature determination, the process may end.

As can be appreciated by one of skill in the art after consideration ofthe present disclosure, the determination of the temperature of anunderwater structure 204 adjacent a control point 1104 or 1404 can beperformed as part of performing a scan of an underwater scene using amonitoring system 304 that incorporates a temperature measurementsub-system 702 as described herein. The processes of measuringtemperature and vibration in accordance with embodiments of the presentdisclosure are similar, in that they both can include taking a series ofmeasurements at a constant azimuth angle and a constant elevation anglerelative to the monitoring system 304. Accordingly, embodiments of thepresent disclosure can be characterized by operating a lidar device 600such that it dwells at a particular angular location until a selectednumber of measurements have been made, or until a series of rangemeasurements have been made over a selected period of time. Inaccordance with further embodiments of the present disclosure, themonitoring system 304 can be operated in a calibration mode, in which atemperature measurement taken by the temperature measurement sub-system702 of the monitoring system 304 at close range is calibrated bycomparing that temperature to a temperature detected by a conventionaltemperature sensor, such as may be included as part of a CTD device 642,included as part of the monitoring system 304. Alternatively or inaddition, the monitoring system 304 can be directed to take atemperature measurement using the temperature measurement sub-system 702from the vicinity of a temperature sensor carried by another monitoringsystem 304, a vehicle 324, or other known temperature location.Moreover, a CTD device 642 can provide a baseline for temp and salinity.The Raman spectral return and the depolarization ratio are both known toalso have a dependence upon salinity, which adds uncertainty to thetemperature measurement. By measuring temperature and salinity at aknown location in the water and comparing the lidar returns near thatsame location, the remote temperature sensor can be calibrated for anabsolute measurement. The temperature measured by the monitoring system304 at the point of interest can then be compared to this knowntemperature to provide an absolute delta. In accordance with furtherembodiments of the present disclosure, background or ambient light canbe subtracted to improve the signal to noise performance.

With reference now to FIG. 18, aspects of a process in accordance withembodiments of the present disclosure for the detection of leaks from anunderwater structure are depicted. Initially, at steps 1804-1820, aprocess that is the same as or similar to the processes described inconnection with FIGS. 9, 13, and 17 is performed. Accordingly, aninitial scan of an underwater scene is taken using a monitoring system304 (step 1804), a manual or autonomous determination is made as towhether a desired underwater structure or portion of a structure 204 iswithin the scene (step 1808), and the field of view is changed if thedesired underwater structure 204 is not within the field of view (step1812). A high-resolution scan of the structure is then taken (step1816), a control point or set of control points 1104 or 1404 isidentified, with location information regarding those control points1104 or 1404 being stored in data storage 824 or memory 764 or 812 (step1820). In accordance with embodiments of the present disclosure, thecontrol point or set of control points 1104 or 1404 in connection withleak monitoring concerning a particular underwater structure 204 arelocated at intervals along that structure 204 or a portion of thestructure, or at a particular point or points on the structure 204 wherethere is a possibility of leaks, such as along or in areas in whichpipes, conduits, tanks, pumps, or other fluid containing structures arelocated.

At step 1824, the lidar measurement system 304 is controlled so that areturn signal is obtained from an area adjacent a selected control pointor area. For example, a return signal can be received from a directioncorresponding to or off-axis from a first one of the control points 1104or 1404, to obtain a measurement in the area immediately above theselected control point. Thus, as for a temperature measurement, thelidar device 600 can be controlled to obtain returns near, but not on,the underwater structure 204. The intensity of the return signal asreceived at the primary receiver 744 can be used in connection with theleak detection process.

A determination is then made as to whether a selected number of rangemeasurements relative to the selected control point have been made (step1828). In general, a leak is indicated by a plume of liquid or gasbubbles having a density that is different than the underwater structure204 or the surrounding water. This appears as a return having adifferent amplitude than the water or the underwater structure 204, andcan be identified in the point cloud data obtained from a highresolution scan of an area by, for example, an automated processimplemented by application software 763 or 832, or by a user monitoringa visualization of the point cloud data generated by the software andpresented by a user output device 820, as depicted in FIG. 19, where theunderwater structure 204 is an area of the seafloor. In accordance withembodiments of the present disclosure, the returns obtained while themonitoring system 304 is dwelling at and collecting returns from aparticular azimuth and elevation angle for a specific range or rangeinterval for purposes of temperature measurement can be used for thesimultaneous detection of leaks. In particular, the portion of thereturn directed to the temperature measurement sub-system 702 by theprimary beam splitter 740 can be used to measure temperature at the sametime the portion of the return directed to the primary receiver 744 bythe beam splitter 740 is used to detect leaks. After the selected numberof range measurements from an area adjacent the underwater structure 204have been made, an indication as to whether leak has been detected canbe output to a user through an output device 820, transmitted to anothersystem, and/or stored (step 1832).

At step 1836, a determination can be made as to whether leak detectionrelative to an underwater structure 204 adjacent other control pointsshould be performed. If so, the process can select the next controlpoint (step 1840), and the process can return to step 1824. If it isdetermined at step 1836 that no other control points 1104 or 1404 in aset remain for leak detection, the process may end.

In another embodiment of the invention, a high-resolution scan oralternately a low-resolution scan is taken of an area. In general, aleak is indicated by a plume of liquid or gas bubbles having a densitythat is different than the underwater structure 204 or the surroundingwater. This appears as a different return having a different amplitudethan the water or the underwater structure 204, and can be identified inthe point cloud data. Therefore, the point cloud from a low, medium, orhigh-resolution scan can be analyzed for plume detection, thusindicating a leak. The plume can then be analyzed to locate a leaksource and higher resolution scans can then be made of a specificleaking structure. The leak detection system can be mounted on a staticplatform like a stationary ROV, tripod, or subsea frame 624.Alternately, the point cloud data can be collected from a movingplatform such as a moving ROV, AUV, or surface vessel (for shallow waterdeployments). The point cloud from either of these collection methodscan be analyzed for leaks.

As can be appreciated by one of skill in the art after consideration ofthe present disclosure, the detection of leaks from an underwaterstructure 204 adjacent a control point 1104 or 1404 can be performed aspart of performing a scan of an underwater scene using a monitoringsystem 304. Moreover, the scan can also be used in connection withperforming movement, vibration, and/or temperature measurements asdescribed herein. It should also be apparent that various measurementscan be made by operating a monitoring system 304 such that it dwells ata selected azimuth angle and elevation angle and takes a series of rangemeasurements. Moreover, a series of range measurements can be used todetect movement and vibration of an underwater structure 204. Where themonitoring system 304 includes a temperature monitoring sub-system 702,the monitoring system can simultaneously determine the temperature ofwater adjacent an underwater structure 204, and detect leaks from thatstructure 204.

In an example use scenario, a user at a monitoring and control station804 directs a monitoring system 304 to image an underwater scene in 3-Dusing a lidar device 600, or to take an image of the scene in 2-D usinga camera 636, or both. The user than selects control points 1104 or 1404on an underwater structure 204 within the imaged scene. Control pointscan also be selected through automated process, such as imagerecognition process, that identify the centroid of the underwaterstructure 204 or components of that structure, or that identifyparticular features of the underwater structure 204. The locations ofthese control points 1104 or 1404 are recorded as points in 3-D space.The monitoring system 304 takes a series of range measurements for eachcontrol point 1104 or 1404. More particularly, for vibration monitoring,a series of range measurements are taken for a first control point alongthe azimuth angle and elevation angle for that control point at least atthe time the control point 1104 or 1404 was defined. Any differences inthe ranges determined within the series of ranges can be applied todetermine the amplitude and frequency of the vibration thus indicated.The monitoring system 304 can control the included scanning device 724so that a series of range measurements can be taken along the azimuthangle and elevation angle associated with a next control point 1104 or1404. A vibration mode for the underwater structure 204 can becalculated from an aggregation of the measurements taken from multiplecontrol points 1104 or 1404 on the structure 204 within a suitably shortperiod of time.

Continuing the example use scenario, for location monitoring, thelocations of the defined control points 1104 or 1404 can be periodicallydetermined from point cloud data encompassing the control points 1104 or1404. More particularly, the point cloud data can be analyzed byautomated processes, implemented by the execution of software 763 by theprocessor 748, and/or the execution of software 832 by processor 808, toidentify the centroid of the underwater structure 204 or a componentthereof, a unique contour or other feature on the underwater structure204, or the location of the center of a lidar target 308 or 312corresponding to the control point 1104 or 1404. A determination canthen be made as to whether the azimuth angle, elevation angle, or rangeto the control point 1104 or 1404 has changed over time. In accordancewith at least some embodiments of the present disclosure, the relativelocations of multiple control points 1104 or 1404 as determined during aprior scan can be compared to their relative locations during asubsequent scan to detect movement and to verify the identity of aparticular control point 1104 or 1404.

Still continuing the example use scenario, the temperature of waterimmediately adjacent or near the underwater structure 204 can bemeasured by operating the lidar device 600 or the monitoring system 304to measure the ratio of the return intensity of different wavelength ordifferent polarization returns at an azimuth angle, elevation angle, andrange corresponding to a point that is near, but not directly on, theunderwater structure. For example, the temperature measurement can bemade from a point that is immediately above or in front of a selectedcontrol point 1104 or 1404. Several hundreds or thousands ofmeasurements can then be made in sequence to obtain an average ratio ofthe strengths of the different wavelengths or polarizations to obtain anaverage that can be used to determine a temperature of the underwaterstructure 204 in an area adjacent the point from which the measurementsare made. For example, and as can be appreciated by one of skill in theart after consideration of the present disclosure, the temperature ofthe underwater structure 204 can be calculated from the temperature ofthe water as determined by operation of the temperature subsystem 702 ofthe monitoring system 304, and from the temperature of the waterimmediately adjacent the monitoring system 304, as determined from adirect temperature sensor provided as part of a CTD device 642 connectedto or included as part of the monitoring system 304.

Leak detection can also be performed as part of the example usescenario. Specifically, point cloud data from the water over or adjacentan underwater structure 204 can include return intensity informationthat differs from that of undisturbed water or from the underwaterstructure 204 itself. In particular, the return from undisturbed waterwill have a relatively lower intensity and the underwater structure 204itself will have a relatively higher intensity than a plume of fluid orbubbles formed as a result of a leak. The intensity data can beanalyzed, for example by comparing returns from points within a selectedvolume of water surrounding a portion of an underwater structure 204containing a fluid, to determine whether a plume of escaping fluid ispresent.

The methods and systems described herein can enable monitoring themovement and displacement of underwater structures 204 over time,including X, Y, Z movement and angular tilts; vortex induced vibrationmonitoring; movement of the subsea tree; water hammer kick detectionduring drilling and production operations; kick detection caused byrapid flow rate changes of production fluids or hydrocarbons duringdrilling and production operations; top hat structure rotationalalignment monitoring; subsidence relative to monuments or otherstructures and vertical well or tree growth; and monitoring andvalidation of paddle or valve positions, and gauge positions. Vibrationmonitoring using embodiments of the present disclosure can be performedin connection with subsea pipes, pumps, or other components from one ormore static or moving monitoring systems 304. In addition, measurementsfrom multiple locations along an underwater structure 204 can be used tomake the vibration mode measurements. Leak detection using embodimentsof the present disclosure can include the detection of hydrocarbons,drilling fluids and other fluids, such as glycol and hydraulic fluids,used to operate and test subsea infrastructure. Volume or surface changemeasurements of underwater structures 204 or the seabed can also beperformed using embodiments of the present disclosure. Thesemeasurements can include anode volume calculations and comparisons overa time period for indication of external and internal corrosion, and fordetermining the remaining useful life of anodes. Seabed volumemeasurements can be made for drill cuttings, scour, and/or subsidence.Reservoir over pressure from well injection and stimulation can bedetected using embodiments of the present disclosure by monitoring theseafloor for cracks or deformations, as well as seepage from methane gasbubbles and other hydrocarbons. This phenomenon is depicted in FIG. 19,which depicts gas bubbles seeping from a crack in the seafloor alongwith seafloor deformation. The temperature of different underwaterstructures 204 can also be taken using embodiments of the presentdisclosure by measuring the temperature of water surrounding theunderwater structure 204.

Various measurements enabled by embodiments of the present disclosureare made possible by the unique, staring nature of the monitoring system304 in at least some operating modes. For instance, by taking a seriesof range measurements along a line over a period of time as part ofdetecting and measuring vibration, a monitoring system 304 as describedherein can also detect transient events, such as kick or hammer events.The acquisition of a series of range measurements from multiple pointsalso enables the detection of a vibration mode in an underwaterstructure 204. Temperature measurements and leak detection monitoringare facilitated by obtaining a series of returns from areas around anunderwater structure 204. In addition, by obtaining and storing accuratelocation information regarding multiple control points, detection ofvalve or other configurable component positions, and rotation ofcomponents is possible.

FIG. 20 depicts a monument 316 that can be used in connection with themonitoring of an underwater structure 204 in accordance with embodimentsof the present disclosure. The monument 316 features three-dimensional308 and/or two-dimensional 312 targets. In accordance with furtherembodiments, the monument 316 can include additional indicia, such asscales 2004. Such indicia can assist in determining visually whether themonument 316 itself or the surrounding seafloor or structure 204 hasmoved. A monument 316 can also provide a reference point with respect towhich the relative location of an underwater structure 204 and/or themonitoring system 304 itself can be determined and monitored. Inaccordance with still further embodiments of the present disclosure, themonument 316 can include an acoustic compatt 2008 to enable the acousticvalidation of the location of the monument 316. The acoustic compatt2008 therefore allows for an independent validation measurement using adifferent measurement mechanism (acoustic versus optical). Accordingly,one or more monuments 316 can be positioned within a scene to providefixed reference points that can be accurately identified by themonitoring system 304 and that can be used as reference points todetermine movement of underwater structures 204 relative to themonuments 316.

As can be appreciated by one of skill in the art after consideration ofthe present disclosure, a monitoring system 304 as described hereinenables the acquisition of various parameters concerning underwaterstructures 204 remotely, from some nonzero standoff distance, withoutrequiring physical contact with such structures, and without requiringintegrating or retrofitting sensors that must be mounted to theunderwater structure 204. Embodiments of a monitoring system 204 areparticularly advantageous because they provide for non-touchmeasurements, reduced tooling requirements, improved accuracy, andimproved flexibility.

The parameters that can be monitored by a monitoring system 304 asdisclosed herein can include the actual location and disposition of astructure 204, whether the structure 204 has moved, whether thestructure 204 is vibrating, the temperature of the water immediatelysurrounding the structure 204, and whether a fluid is leaking from thestructure 204. In addition, embodiments of the present disclosureprovide a monitoring system 304 and methods that permit the simultaneousor near simultaneous acquisition of data regarding such parameters. Forexample, the acquisition of a set of range information along a linedescribed by a particular azimuth angle and elevation angle can be usedto detect vibration within a structure 204 intersected by that line, andan average of that range information can also be used to determine thelocation of that structure 204 at a control point 1104 or 1404 locatedon that structure 204. In addition, the monitoring system 304 can becontrolled to obtain sets of range measurements from multiple locations(e.g. control points 1104 or 1404) along a structure 204 in fastsuccession in virtually the same time, which can be used to calculatethe vibration mode of the structure 204. As another example, a returnreceived at the monitoring system 304 from an azimuth angle, elevationangle, and range corresponding to a location immediately adjacent anunderwater structure 204 can be simultaneously provided to a primaryreceiver, and used in connection with leak detection, and to first 756and second 760 temperature channel receivers and used in connection withmeasuring the temperature of the water at that location. Accordingly, asingle monitoring system 304 placed and operated in the vicinity of anunderwater structure 204 can provide monitoring and metrology withrespect to multiple underwater structures 204, without requiring contactwith those structures 204.

As described herein, a monitoring system 304 can be implemented as asingle spot sensor system, such as a scanning lidar, or a lidar thatreceives and senses returns from multiple points within a scene insimultaneously. In a monitoring system 304 implemented as a single spotsensor system, measurements from different points within a scene can bemade at virtually the same time, by sequentially pointing the lidardevice 600 of the monitoring system 304 at different points within thescene in an automated fashion. In a monitoring system 304 implemented asa flash sensor system, measurements from different points within a scenecan be made at the same time (i.e. multiple measurements can be obtainedfrom returns generated from a single pulse of light 704), with returnsreceived at different pixels within the sensor corresponding todifferent azimuth angles and elevation angles relative to the monitoringsystem 304. The monitoring system 304 can be mounted on an ROV, AUV,tripod, monument, cage, or other subsea structure. In at least someembodiments, a cage or frame 624 to which a monitoring system 304 ismounted can itself comprise an underwater structure, and can provide aplatform with numerous selectable functions. This can include theincorporation of batteries and a power control system that allows forlong-term autonomous deployment. The monitoring system 304 can alsoprovide additional capabilities, including, but not limited to, datastorage and backup, temperature sensors, depth sensors, salinitysensors, other chemical sensors, and communication devices. Themonitoring system 304 can also provide timing signals between multiplesensors to time synchronize the data collection of those sensors.Examples of communication devices include wired electrical or opticalsystems, a radio frequency, free space optical, or acoustic devices.Communications can be with ROV's, AUVs, resident vehicles, otherintelligent structures in the field, or the surface. The monitoringsystem 304 can store data, compress and send out data samples, or autoprocess data to look for change detection and send alarms signals whenchange is detected. Moreover, a monitoring system 304 can provide power,data storage, and communications capabilities to other monitoringdevices or monitoring systems 304, for example to allow for monitoringat different angles or over an increased field of view. Alternatively orin addition, the monitoring system 304 can be connected to the localinfrastructure for power and/or communications.

In accordance with still other embodiments of the present disclosure, a3-D point cloud comprising data obtained by a monitoring system 304 canencompass portions of an underwater scene that include multipleunderwater structures 204, monuments 316, additional monitoring systems304, three-dimensional targets 308, two dimensional targets 312, andother structures or features within a field of regard 328 of themonitoring system 304. The relative locations of such features can beused in connection with detecting the movements of the features relativeto one another. Moreover, by incorporating monuments 316,three-dimensional targets 308, two-dimensional targets 312, and controlpoints 1104 and 1404 that have known locations relative to an absolutereference system, tracking the relative locations of underwaterstructures 204 can be performed by different monitoring systems 304, orby monitoring systems 304 that have themselves been repositioned betweendifferent point cloud data acquisition sessions or during point cloudacquisition sessions.

In at least some embodiments of the present disclosure, a human operatoror user interacts with the monitoring system 304 through a monitoringand control station 804 that is in operative communication with themonitoring system 304. The user can control the field of regard 328 ofthe monitoring system 304 by entering control commands through a userinput 816 to direct a movable platform or vehicle 324 carrying themonitoring system 304, and/or to direct a pan and tilt head 604 to whicha lidar device 600 or the monitoring system 304 itself is mounted. Inaddition, real time or near real-time feedback regarding the field ofregard 328 of the monitoring system 304 can be provided to the userthrough the user output 820. Moreover, the feedback provided by the useroutput 820 can be in the form of a two-dimensional image obtained by acamera 636, a visualization of point cloud data obtained by a lidardevices 600, or a synthesis of two-dimensional and three-dimensionaldata.

In accordance with still other embodiments of the present disclosure, amonitoring system 304 can operate autonomously or semi-autonomously. Forexample, in an autonomous mode, the monitoring system 304 can scan ascene to obtain point cloud data, and can execute software to detect andidentify an underwater structure 204 of interest. The monitoring system304 can further identify control points on the structure 204, and canobtain data relative to those control points. Examples of such controlpoints include particular features on the underwater structure 204,three-dimensional 308 and two dimensional 312 targets, points taken atintervals along the underwater structure 204, or the like. In asemi-autonomous mode, a user can provide direction to the monitoringsystem 304, such as defining the limits of a scene or features within ascene comprising an underwater structure 204 for which monitoring is tobe performed. Alternatively or in addition, a user can define a featureon a structure 204, such as a surface, to be monitored, and themonitoring system 304 can define control points within the surface foruse in connection with the monitoring. As yet another example, a usercan manually identify features or targets 308 or 312, for example bycontrolling a cursor presented in association with a visualization ofpoint cloud data, and the monitoring system 304 can precisely define thelocation of the selected control point 1104 or 1404 by identifying thecenter or centroid of the target 308 or 312, the edge of a feature, orother distinguishing indicia or feature at or near the user selectedlocation.

As can also be appreciated by one of skill in the art afterconsideration of the present disclosure, various functions can bedistributed amongst different components of a monitoring system 304 ordifferent connected systems or devices. For example, the processor 748located within an underwater pressure vessel 700 of a monitoring system304 can execute application software 763 that controls an associatedlidar device 600 to obtain raw point cloud data comprising azimuthangle, elevation angle, range, intensity, and timestamp information. Theinformation generated by such onboard processing can then be transmittedby the communications interface 768 to a monitoring and control station804. Alternatively or in addition, onboard processing performed by themonitoring system 304 can provide automatic notifications or alarms thatare transmitted to the monitoring and control station 804 or otherfacility. The monitoring and control station 804 receives the pointcloud data, notifications, alarms, or other information transmitted bythe monitoring system 304 through a communication interface 828, andstores the point cloud data 840 in data storage 824. The processor 808can then execute system application software 832 to present avisualization of the point cloud data through a user output device 820.The processor 808 can further execute system application software 832 tocompare point cloud data obtained at different times for the detectionof movement, vibration, or leaks. Moreover, point cloud data can beaveraged by operation of the processor 808, to provide more accuratelocation and temperature information. In accordance with still otherembodiments of the present disclosure, such postprocessing of pointcloud data can be performed by the monitoring system 304 itself, byservers or control stations provided in place of or in addition to themonitoring and control station 804, or in various combinations.

Embodiments of the present disclosure provide systems and methods thatenable a single instrument (i.e. a lidar device 600 provided as part ofa monitoring system 304) to obtain information regarding multipleparameters concerning an underwater structure 204. Accordingly, thedifficulties associated with coordinating and calibrating multipleinstruments to make such multiple measurements, as may have been donepreviously, are avoided. Embodiments of the present disclosure furtherprovide a unique interface (or application programming interface (API)),for example as provided through execution of application software 763and/or 832, to perform the multiple measurements using the singleinstrument. In a general operating mode, an initial scan of a scene istaken that is quickly processed and displayed to a user through adisplay screen provided as part of a user output device 820. The initialimage can then be used to identify target areas of interest. The initialimage can be created using three-dimensional point cloud data ortwo-dimensional data. Moreover, the two-dimensional data can be derivedfrom three-dimensional data obtained by a lidar device 600, or from atwo-dimensional camera 636. In either case, the azimuth and elevationangles at a recorded time are known for each point and can be used torevisit those exact locations on the target or underwater structure 204,for example to confirm that the associated underwater structure 204 hasnot moved, to detect vibration, and to take temperature measurementsrelative to known locations. In addition, control points 1104 or 1404that correspond to targets 308 or 312, or particular structuralfeatures, and the spatial relationship between the targets 308 or 312and particular features, are recorded and can be used in connection withdetecting movement of the underwater structure. In at least someembodiments, the user can select an area or areas within the image bybanding or by identifying multiple points on the image. The user canthen specify what operations are to be performed upon the selected area.These operations can include some or all of the following:high-resolution scanning, including locating the underwater structure204 or features thereof in three-dimensional space; vibrationmeasurements; temperature measurements; and leak detection. Themonitoring system 304 can then be operated to automatically make themeasurements within or, for temperature and leak detection purposes,within the vicinity of the specified area.

In accordance with at least some embodiments of the present disclosure,the technology encompasses:

(1) A method for monitoring an underwater structure, comprising:

taking a first three-dimensional scan of an underwater scene using afirst monitoring system, wherein a first set of point cloud data isproduced from the first three-dimensional scan, wherein locations of atleast some points on the underwater structure are included in the firstset of point cloud data;

identifying a first control point on the underwater structure to bemonitored, wherein the first control point has a first three-dimensionallocation that corresponds to a first point included in the first set ofpoint cloud data;

a first selected period of time after taking the first three-dimensionalscan, using the first monitoring system to obtain a secondthree-dimensional location of the first control point on the underwaterstructure; and

comparing the first three-dimensional location to the secondthree-dimensional location to determine whether the underwater structurehas moved.

(2) The method of (1), wherein the three-dimensional locations compriseazimuth angle, elevation angle, intensity, and range measurements

(3) The method of (2), wherein making the measurements includes at leastone of measuring a voltage, a time, a frequency, a phase, a number ofsamples, a number of digits, a pixel count, or a fringe count.

(4) The method of (2) or (3), wherein the measurements are made by atleast one of laser scanning, ladar, flash ladar, laser triangulation,photometric stereo, stereoscopic vision, structured light,photoclinometry, stereo-photoclinometry, holographic systems, amplitudemodulated continuous wave (AMCW) phase detection, chirped AMCW,amplitude frequency modulated continuous wave (FMCW) detection, trueFMCW, pulse modulation codes, time of flight pulse detection.

(5) The method of (2) to (4), wherein the measurements are made by atleast one of a scanning system device or a multi-detector device or 2-Dor 3-D camera in which each detector pixel equates to an angle.

(6) The method of any of (1) to (5), further comprising:

taking a first series of range measurements from the first monitoringsystem along a first line corresponding to a first azimuth angle and afirst elevation angle, wherein the first line intersects the underwaterstructure;

comparing a plurality of the range measurements within the first seriesof range measurements to determine whether the underwater structure isvibrating.

(7) The method of (6), further comprising:

determining an amplitude and a frequency of vibration of the underwaterstructure at the intersection of the first line and the underwaterstructure.

(8) The method of (6) or (7), further comprising:

taking a second series of range measurements from the first monitoringsystem along a second line corresponding to a second azimuth angle and asecond elevation angle, wherein the second line is not parallel to thefirst line, and wherein the second line intersects the underwaterstructure;

determining an amplitude and a frequency of vibration to the underwaterstructure at the intersection of the second line and the underwaterstructure.

(9) The method of (8), further comprising:

determining a mode of vibration of the underwater structure.

(10) The method of any of (1) to (9), further comprising:

receiving a first series of return signals from a first point located inwater surrounding the underwater structure, wherein the first point islocated along a second azimuth angle, a second elevation angle, and at asecond range relative to the first monitoring system, and wherein thefirst point is not located on the underwater structure;

for each of the return signals in the first series of return signals,determining a ratio of a first component of the return signal to asecond component of the return signal;

determining a temperature of the water at the first point from aplurality of the determined ratios.

(11) The method of (10), wherein for each of the return signals in thefirst series of return signals the first component includes light of afirst wavelength and the second component includes light of a secondwavelength.

(12) The method of (10), wherein for each of the return signals in thefirst series of return signals the first component includes light of afirst polarization and the second component includes light of a secondpolarization.

(13) The method of any of (10) to (12), wherein at least one oftemperature and salinity measurements from a point sensor are used tocalibrate the temperature measurement made from the plurality of thedetermined ratios.

(14) The method of (13), wherein the temperature measurement from thepoint sensor are compared to a temperature measurement made from aplurality of determined ratios obtained at a range gate that is closestto the point sensor and away from the range gate of the structure ofinterest.

(15) The method of any of (10) to (14), wherein determining a ratio of afirst component of the return signal to a second component of the returnsignal includes providing the first component of the return signal to afirst temperature channel receiver and providing the second component ofthe return signal to a second temperature channel receiver, the methodfurther comprising:

for each of the return signals in the first series of return signals,providing a portion of the return signal to a primary receiver.

(16) The method of any of (1) to (15), further comprising:

determining from a plurality of series of return signals from aplurality of points located in the water surrounding the underwaterstructure a fluid is leaking from the underwater structure.

(17) The method of (16), wherein the fluid is at least one of liquidhydrocarbons, gas hydrocarbons, drilling fluid, glycol, hydraulic fluid,or other fluids used to operate and test subsea infrastructure, whereinthe leak monitoring is performed during pre-commissioning pressuretests, other tests, or normal operations.

(18) The method of (16) or (17), wherein leak monitoring is performedfor reservoir over pressure from well injection and stimulation bymonitoring for seepage from methane gas bubbles and other hydrocarbons.

(19) The method of any of (1) to (18), wherein the first control pointcorresponds to a centroid of a feature of the underwater structure.

(20) The method of any of (1) to (18), wherein the first control pointcorresponds to a target placed on the underwater structure.

(21) The method of any of (1) to (20), wherein the first and secondthree-dimensional locations of the first control point on the underwaterstructure is a location of a centroid of the control point.

(22) The method of any of (1) to (21), further comprising:

identifying a second control point in the underwater scene, wherein thefirst three-dimensional location of the first control point has a firstlocation relative to the second control point, wherein the secondthree-dimensional location of the first control point has a secondlocation relative to the second control point; and

generating an indication that the underwater structure has moved whenthe first location relative to the second control point is differentthan the second location relative to the second control point.

(23) The method of (22), wherein the indicated movement includes atleast one of the following:

movement and displacement of the underwater structure, includingmovement in X, Y, Z planes and angular tilt;

vortex induced vibration;

movement of a subsea tree;

displacement caused by water hammer events during drilling andproduction;

kick events caused by rapid flow rate changes or production fluids orhydrocarbons during drilling and production;

top hat structure rotational alignment changes;

subsidence relative to monuments, other structures, seabed artifacts,and vertical well or tree growth;

paddle position movement;

valve position movement; and

gauge position.

(24) The method of any of (1) to (22), wherein a volume or surface of anunderwater structure is monitored over time using a plurality of seriesof return signals from a plurality of points located in the scene todetect change, wherein the measurements include measurements of at leastone of: anode volume for indications of corrosion; seabed volumemeasurement for drill cutting, scour, or subsidence; and seabed cracksor deformations due to reservoir over pressure from well injection andstimulation.

In accordance with further aspects of the present disclosure, thetechnology encompasses:

(25) A method of monitoring an underwater structure, comprising:

a light source and a receiver of a monitoring system along a first linehaving a first azimuth angle and a first elevation angle relative to themonitoring system, wherein the first intersects the underwater structureat least at a first point in time;

taking a first series of range measurements along the first line;

comparing a first one of the range measurements included in the firstseries of range measurements to a second one of the range measurementsin the first series of range measurements; and

outputting an indication of a status of the underwater structure.

(26) The method of (25), wherein the first series of range measurementsare taken in series, the method further comprising:

deriving a first frequency of vibration from the first series of rangemeasurements, wherein an indication that the underwater structure isvibrating is output.

(27) The method of (25) or (26), further comprising:

directing the light source and the receiver of the monitoring systemalong a second line having a second azimuth angle and a second elevationangle relative to the monitoring system;

taking a second series of range measurements along the second line;

comparing a first one of the range measurements included in the secondseries of range measurements to a second one of the range measurementsincluded in the second series of range measurements;

deriving a second frequency of vibration from the second series of rangemeasurements; and

deriving a vibration mode of the underwater structure from the first andsecond series of range measurements.

(28) The method of any of (25) to (27), further comprising:

directing the light source and the receiver of the monitoring systemalong a second line having a second azimuth angle and a second elevationangle relative to the monitoring system;

receiving a series of return signals from a point along the second lineand at a selected range from the monitoring system, wherein the point islocated in water surrounding the underwater structure;

determining a temperature of the water at the point;

outputting an indication of the temperature of the underwater structure.

In accordance with still other aspects of the present disclosure, thetechnology encompasses:

(29) A system for detecting movement of an underwater structure,comprising:

a monitoring system, including:

-   -   a receive telescope;    -   a first beam splitter, wherein the first beam splitter is        located along a first optical path defined by the receive        telescope, and wherein the first beam splitter defines a range        return signal optical path and a temperature return optical        path;    -   a primary receiver, wherein the primary receiver is located        along the range return signal optical path;    -   a second beam splitter, wherein the first beam splitter is        located along the range return signal optical path, and wherein        the second beam splitter defines a first temperature channel        optical path and a second temperature channel optical path;    -   a first temperature channel receiver, wherein the first        temperature channel receiver is located along the first        temperature channel optical path;    -   a second temperature channel receiver, wherein the second        temperature channel receiver is located along the second        temperature channel optical path.

(30) The system of (29), further comprising:

a user interface system, including:

-   -   a user input;    -   a user output;    -   memory;    -   a communication interface;    -   a processor, wherein the user interface system processor is        operable to execute application software stored in the user        interface system memory to present a visualization of point        cloud data obtained by the laser monitoring system through the        user output, and to receive input from the user through the user        input, wherein the input includes a selection of a control        point;    -   wherein the monitoring system further includes:        -   a light source;        -   a processor;        -   memory;        -   a communication interface,            -   wherein the monitoring system processor is operable to                execute application software stored in the monitoring                system memory to operate the light source and the                primary receiver to obtain three-dimensional location                data, including three-dimensional location data of the                underwater structure, and            -   wherein the monitoring system processor is operable to                execute application software stored in the monitoring                system memory to operate the light source and the first                and second temperature channel receivers to obtain                temperature data from water at a selected range from the                monitoring system.

The foregoing discussion has been presented for purposes of illustrationand description. Further, the description is not intended to limit thedisclosed systems and methods to the forms disclosed herein.Consequently, variations and modifications commensurate with the aboveteachings, within the skill or knowledge of the relevant art, are withinthe scope of the present disclosure. The embodiments describedhereinabove are further intended to explain the best mode presentlyknown of practicing the disclosed systems and methods, and to enableothers skilled in the art to utilize the disclosed systems and methodsin such or in other embodiments and with various modifications requiredby the particular application or use. It is intended that the appendedclaims be construed to include alternative embodiments to the extentpermitted by the prior art.

What is claimed is:
 1. A system, comprising: a light source; a window; aprimary beamsplitter; a primary receiver; a secondary beamsplitter; afirst temperature channel receiver; and a second temperature channelreceiver, wherein light output from the light source is passed by thewindow to a scene exterior to the system, wherein light reflected fromthe scene exterior to the system is passed by the window to the primarybeamsplitter, wherein the primary beamsplitter divides the reflectedlight into a first portion that is sent to the primary receiver and asecond portion that is sent to the secondary beamsplitter, and whereinthe secondary beamsplitter divides the second portion of the reflectedlight into first and second channels, wherein light in the first channelis received at the first temperature channel receiver, and wherein lightin the second channel is received at the second temperature channelreceiver.
 2. The system of claim 1, further comprising: a firstnarrowband filter; and a second narrowband filter, wherein light in thefirst channel is passed through the first narrowband filter before it isreceived at the first temperature channel receiver, wherein light in thesecond channel is passed through the second narrowband filter before itis received at the second temperature channel receiver, wherein thefirst narrowband filter has a pass band encompassing a first Ramanwavelength, and wherein the second narrowband filter has a pass bandencompassing a second Raman wavelength.
 3. The system of claim 1,further comprising: a first quarter wave plate, wherein the firstquarter wave plate is in an optical path between the window and theprimary beamsplitter; and a second quarter wave plate, wherein thesecond quarter wave plate is in an optical path between the primarybeamsplitter and the secondary beamsplitter, wherein the secondarybeamsplitter is a polarization beamsplitter, wherein the light in thefirst temperature channel has a first polarization, and wherein thelight in the second temperature channel has a second polarization. 4.The system of claim 1, further comprising: a receive telescope, whereinthe receive telescope is in an optical path between the window and theprimary beamsplitter; and a shutter, wherein in the shutter is locatedin an optical path between the window and the primary beamsplitter, andwherein the shutter is operable as a range gate for light reflected fromthe scene exterior to the system.
 5. A method, comprising: generatinglight; directing the light toward an underwater scene; receiving areturn signal from the underwater scene; and at least one of measuring atemperature of water in the underwater scene or measuring a motion of astructure in the underwater scene.
 6. The method of claim 5, wherein arange to a structure in the underwater scene and the temperature ofwater in the underwater scene is measured.
 7. The method of claim 6,wherein the range to a structure in the underwater scene and thetemperature of water in the underwater scene are measured from a singlereturn signal returned from the underwater scene along a first line ofsight.
 8. The method of claim 6, wherein the range to a structure in theunderwater scene and the temperature of water in the underwater sceneare measured from a plurality of return signals returned from theunderwater scene along a first line of sight.
 9. The method of claim 6,wherein the temperature of the water is measured at a selected positionfrom a system in which the light is generated and at which the returnsignal is received.
 10. The method of claim 6, further comprising:gating the return signal, wherein only a portion of the return signalfrom a selected range is received.
 11. The method of claim 6, whereinthe range to a structure in the underwater scene is measured from areturn signal returned from along a first line of sight, wherein thetemperature of water in the underwater scene is measured from a returnsignal returned from a point along a second line of sight, wherein thepoint along the second line of sight is adjacent the underwaterstructure from which the return signal from the scene from along thefirst line of sight is reflected, and wherein the temperature of thewater in the scene at the point along the second line of sight ismeasured adjacent the underwater structure.
 12. The method of claim 5,further comprising: for each return signal received from the underwaterscene, determining a ratio of a first component of the return signal toa second component of the return signal, and determining a temperatureof the water from the determined ratio.
 13. The method of claim 12,wherein at least one of temperature and salinity measurements from apoint sensor are used to calibrate the temperature measurement.
 14. Themethod of claim 13, wherein the temperature measurement from the pointsensor is compared to a temperature measurement made from a determinedratio obtained at a range gate that is closest to the point sensor andaway from a range gate of the structure.
 15. The method of claim 5,wherein at least one of: the temperature is measured adjacent or downthe opening of a well in the underwater scene to monitor a temperatureat the top of the well plug or internal pipe sealing plug as part of anabandonment operation, during reservoir stimulation/carbon reinjection,or during reservoir lifting operations to validate no temperatureincrease at the top of the well; the temperature is measured adjacent ordown the opening of a well in the underwater scene by mounting amonitoring system on a remotely operated vehicle, an autonomousunderwater vehicle, or on a structure that is mounted on top of theunderwater well; or the location of the plug in reference to a point onthe top section of the well casing is monitored as part of anabandonment operation, during reservoir stimulation/carbon reinjection,or during reservoir lifting operations to validate no movement of theplug occurs.
 16. The method of claim 5, wherein the motion of thestructure in the scene is measured from a plurality of rangemeasurements obtained from along a first line of sight to determine afrequency and amplitude of vibration.
 17. The method of claim 5, whereinmotion of a structure in the underwater scene is measured, whereinmeasuring the motion of the structure in the underwater scene includes:taking a first series of range measurements along a first linecorresponding to a first azimuth angle and a first elevation angle,wherein the first line intersects the structure; determining anamplitude and a frequency of vibration of the structure at theintersection of the first line and the structure; taking a second seriesof range measurements along a second line corresponding to a secondazimuth angle and a second elevation angle, wherein the second lineintersects the structure; and determining an amplitude and a frequencyof vibration of the structure at the intersection of the second line andthe structure.
 18. The method of claim 17, further comprising:determining a mode of vibration of the structure.
 19. The method ofclaim 5, wherein the measurements are made using a monitoring systemcarried by an underwater vehicle.
 20. A method, comprising: generatinglight; directing the light toward an underwater scene; receiving areturn signal from a structure in the underwater scene; measuring arange to the structure; and measuring a temperature of water in theunderwater scene.